The present invention relates to orthodontic devices, and more particularly to face bows.
Face bows are utilized in the orthodontic practice generally to gradually drive molar teeth distally and to correct molar protrusions and irregularities and relieve overcrowding of the molar teeth. Quite basically, a face bow comprises an orthodontic device which includes an orally worn inner bow-shaped element designed in accordance with the curvature of the denture. At substantially the outer concave center of the inner bow, an outer extra-oral bow is permanently physically attached to the inner bow. The outer bow is generally longer than the inner bow and has greater radii of curvature. The inner bow is worn along the inside of the mouth and generally is attached to the teeth by means of tubular brackets, known as buccal tubes, mounted to the molar teeth to be moved. Stops, loops or offsets on the inner bow transmit a force to the molar teeth and control the amount of distal movement provided by the face bow. The ends of the outer bow are generally attached to an elastic neck strap or headgear which is worn around the back of the neck or head, depending on the direction of force to be applied. The tension provided by the elastic neck strap or headgear serves to put constant pressure on the teeth to which the inner bow is attached, causing the molars to be moved distally with respect to the anterior teeth and the center of the mouth, thus allowing space for rearward movement of the more anterior teeth.
The use of face bows in the orthodontic art is well known. Face bows do, however, have certain disadvantages. They must be worn for extended periods of time to have an effect and the most likely users are children. The danger thus exists that the face bow might be pulled out of the user's mouth either deliberately or accidentally, while at play, etc. There is thus a danger that the sharp ends and hooks, particularly of the inner bow, might come in contact with the user's skin or eyes, possibly causing lacerations or blindness. There have been several known cases of blindness caused by face bows.
Several devices exist which attempt to solve this safety problem, but they all involve the neck strap or headgear providing for disengagement after the face bow has been moved forward a certain distance. The disadvantage of this type of device is that it might fail to provide sufficient force to move the teeth if not properly adjusted. Another known device uses a hook requiring a rearward movement of the inner bow before disengagement from the teeth. This device makes it more difficult to remove from the mouth, even under normal circumstances, and could result in excessive forces being applied to the teeth should the face bow be accidentally pulled outward.
Accordingly, it is an object of the present invention to provide a face bow which is safe and eliminates the above dangers of the known face bows.
It is a further object of the present invention to provide a face bow having an inner bow which can be permanently wired to the teeth and yet which allows easy removal of the outer bow prior to or during normal activities, such as eating.
It is yet a further object of the present invention to provide a face bow wherein different outer bows can be used with the same inner bow, which may be permanently wired to the teeth.
Conversely, it is an object of the present invention to provide a face bow wherein more than one type of inner bow can be used with the same outer bow.
Furthermore, it is an object of the present invention to provide a face bow which allows the same outer bow to be used with a different inner bow so that when the inner bow requires changing due to growth, breakage or the chemical stress of the oral environment, the same outer bow can be reused, thus extending the life of the outer bow and eliminating some expense.
Furthermore, it is an object of the present invention to provide a face bow which can be easily inserted into the mouth by the user.